In general, a polarizing sheet or a polarizing film has a function of converting natural light into polarized light. Such a polarizing function is realized by a material dyed to a polarizing sheet.
For a liquid crystal display, an iodine type polarizing film dyed with iodine as a polarizing material is generally used. The iodine type polarizing film is manufactured by dyeing a polyvinyl alcohol film with dichromatic iodine or a dichromatic dye and orienting the polyvinyl alcohol film in a predetermined direction using a uniaxial elongating method. The iodine type polarizing film is usually used for LCDs.
The iodine type polarizing film may be manufactured, for example, through a wet type dyeing process of uniaxially elongating a non-elongated polyvinyl alcohol film in an aqueous solution and then dipping the polyvinyl alcohol film in a solution containing iodine or potassium iodide, dipping a non-elongated polyvinyl alcohol film in a solution containing iodine or potassium iodide and then uniaxially elongating the polyvinyl alcohol film, uniaxially elongating a non-elongated polyvinyl alcohol film in a solution containing iodine or potassium iodide, or uniaxially elongating a non-elongated polyvinyl alcohol film in a dry state and then dipping the polyvinyl alcohol film in a solution containing iodine or potassium iodide, or a dry type dyeing process of exposing a polyvinyl alcohol film to iodine steam.
Consequently, there is a high necessity for research into the manufacture of a polarizing film exhibiting improved optical properties through improvement of the dyeing process.